<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>原生事件绑定</title>
</head>

<body>
  <button id="btn1">按钮一</button>
  <button id="btn2">按钮二</button>
  <button onclick="demo()">按钮三</button>

  <script type="text/javascript">

    const btn1 = document.getElementById('btn1')
    btn1.addEventListener('click', () => {
      alert('按钮一被点击了！')
    })

    const btn2 = document.getElementById('btn2')
    btn2.onclick = () => {
      alert('按钮二被点击了！')
    }


    function demo() {
      alert('按钮三被点击了！')
    }

  </script>
</body>

</html>